Implement Phases 1-5: skeleton, OAuth, categories, video sync/feed, playback

- FastAPI + PostgreSQL + Alembic + React/Vite skeleton, Docker Compose, healthcheck
- Google OAuth (single allowed account), encrypted refresh token storage
- Subscriptions sync with pagination, uploads playlist batch fetch
- Categories CRUD, many-to-many channel assignment, category filtering
- Video sync (playlistItems + videos.list batching), cached feed with cursor
  pagination, background scheduler (APScheduler)
- Video detail page with YouTube embed player
- SPA fallback routing, optimistic UI updates, client-side query caching

40 backend tests covering OAuth allow-list, sync idempotency, cascade deletes,
cursor pagination, and category filtering.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

tests/test_sync.py

@@ -0,0 +1,167 @@
+from app.models.channel import Channel
+from app.models.video import Video
+from app.services import sync
+
+
+def _fake_credentials():
+    return object()
+
+
+def test_sync_subscriptions_idempotent_and_unsubscribes(monkeypatch, db_session):
+    monkeypatch.setattr(sync.google_oauth, "get_credentials", lambda db: _fake_credentials())
+    monkeypatch.setattr(
+        sync.youtube_client,
+        "fetch_subscriptions",
+        lambda creds: [
+            {"youtube_channel_id": "chanA", "title": "Channel A", "description": "d", "thumbnail_url": "t"},
+            {"youtube_channel_id": "chanB", "title": "Channel B", "description": "d", "thumbnail_url": "t"},
+        ],
+    )
+    monkeypatch.setattr(
+        sync.youtube_client,
+        "fetch_uploads_playlists",
+        lambda creds, ids: {cid: f"UU{cid}" for cid in ids},
+    )
+
+    result = sync.sync_subscriptions(db_session)
+
+    assert result["status"] == "completed"
+    assert result["channels_added"] == 2
+    assert result["channels_unsubscribed"] == 0
+
+    channels = db_session.query(Channel).order_by(Channel.youtube_channel_id).all()
+    assert [c.youtube_channel_id for c in channels] == ["chanA", "chanB"]
+    assert all(c.subscribed for c in channels)
+    assert channels[0].uploads_playlist_id == "UUchanA"
+
+    # Second sync: chanA disappears from subscriptions, chanC appears.
+    monkeypatch.setattr(
+        sync.youtube_client,
+        "fetch_subscriptions",
+        lambda creds: [
+            {"youtube_channel_id": "chanB", "title": "Channel B", "description": "d", "thumbnail_url": "t"},
+            {"youtube_channel_id": "chanC", "title": "Channel C", "description": "d", "thumbnail_url": "t"},
+        ],
+    )
+
+    result2 = sync.sync_subscriptions(db_session)
+
+    assert result2["channels_added"] == 1
+    assert result2["channels_updated"] == 1
+    assert result2["channels_unsubscribed"] == 1
+
+    channels = {c.youtube_channel_id: c for c in db_session.query(Channel).all()}
+    assert len(channels) == 3
+    assert channels["chanA"].subscribed is False
+    assert channels["chanB"].subscribed is True
+    assert channels["chanC"].subscribed is True
+
+
+def test_sync_in_progress_raises(monkeypatch, db_session):
+    sync._subscriptions_lock.acquire()
+    try:
+        try:
+            sync.sync_subscriptions(db_session)
+            assert False, "expected SyncInProgress"
+        except sync.SyncInProgress:
+            pass
+    finally:
+        sync._subscriptions_lock.release()
+
+
+def _seed_channel(db_session, youtube_channel_id="chanA", uploads_playlist_id="UUchanA"):
+    channel = Channel(
+        youtube_channel_id=youtube_channel_id,
+        title="Channel",
+        subscribed=True,
+        uploads_playlist_id=uploads_playlist_id,
+    )
+    db_session.add(channel)
+    db_session.commit()
+    db_session.refresh(channel)
+    return channel
+
+
+def test_sync_videos_adds_and_updates(monkeypatch, db_session):
+    channel = _seed_channel(db_session)
+
+    monkeypatch.setattr(sync.google_oauth, "get_credentials", lambda db: object())
+    monkeypatch.setattr(
+        sync.youtube_client, "fetch_playlist_video_ids", lambda creds, playlist_id, max_results: ["vid1"]
+    )
+    monkeypatch.setattr(
+        sync.youtube_client,
+        "fetch_videos_details",
+        lambda creds, ids: [
+            {
+                "youtube_video_id": "vid1",
+                "youtube_channel_id": channel.youtube_channel_id,
+                "title": "Video One",
+                "description": "d",
+                "thumbnail_url": "t",
+                "published_at": "2026-09-10T12:00:00Z",
+                "duration_iso8601": "PT5M",
+            }
+        ],
+    )
+
+    result = sync.sync_videos(db_session)
+
+    assert result["status"] == "completed"
+    assert result["videos_added"] == 1
+
+    video = db_session.query(Video).filter_by(youtube_video_id="vid1").one()
+    assert video.title == "Video One"
+    assert video.duration_seconds == 300
+    assert video.youtube_url == "https://www.youtube.com/watch?v=vid1"
+
+    monkeypatch.setattr(
+        sync.youtube_client,
+        "fetch_videos_details",
+        lambda creds, ids: [
+            {
+                "youtube_video_id": "vid1",
+                "youtube_channel_id": channel.youtube_channel_id,
+                "title": "Video One Updated",
+                "description": "d2",
+                "thumbnail_url": "t2",
+                "published_at": "2026-09-10T12:00:00Z",
+                "duration_iso8601": "PT6M",
+            }
+        ],
+    )
+
+    result2 = sync.sync_videos(db_session)
+    assert result2["videos_added"] == 0
+    assert result2["videos_updated"] == 1
+
+    videos = db_session.query(Video).all()
+    assert len(videos) == 1
+    assert videos[0].title == "Video One Updated"
+
+
+def test_sync_videos_skips_unknown_channel(monkeypatch, db_session):
+    _seed_channel(db_session, "chanA")
+
+    monkeypatch.setattr(sync.google_oauth, "get_credentials", lambda db: object())
+    monkeypatch.setattr(sync.youtube_client, "fetch_playlist_video_ids", lambda creds, playlist_id, max_results: [])
+    monkeypatch.setattr(
+        sync.youtube_client,
+        "fetch_videos_details",
+        lambda creds, ids: [
+            {
+                "youtube_video_id": "vidX",
+                "youtube_channel_id": "unknown-channel",
+                "title": "Orphan",
+                "description": "",
+                "thumbnail_url": None,
+                "published_at": "2026-09-10T12:00:00Z",
+                "duration_iso8601": None,
+            }
+        ],
+    )
+
+    result = sync.sync_videos(db_session)
+
+    assert result["videos_skipped"] == 1
+    assert db_session.query(Video).count() == 0